Key to JavaScript Solar Eclipse Explorer
Fred Espenak
Instructions
The JavaScript Solar Eclipse Explorer can compute the local circumstances for every solar eclipse visible from a city for any century from -1499 to 3000 (1500 BCE to 3000 CE). The followig key describes the data found in the local circunstances tables.
Column Heading Definition/Description
1 Calendar Calendar Date at instant of Maximum Eclipse.
Date Gregorian Calendar is used for dates after 1582 Oct 15.
Julian Calendar is used for dates before 1582 Oct 04.
2 Eclipse Eclipse Type where:
Type P = Partial Eclipse.
A = Annular Eclipse.
T = Total Eclipse.
3 Partial Local Time when partial eclipse begins.
Eclipse
Begins
4 Sun Sun's altitude (in degrees) when partial eclipse begins.
Alt
5 A or T Local Time when annular or total eclipse begins.
Eclipse
Begins
6 Maximum Local Time at maximum eclipse.
Eclipse
7 Sun Sun's altitude (in degrees) at maximum eclipse.
Alt
8 Sun Sun's azimuth (in degrees) at maximum eclipse.
Azi
9 A or T Local Time when annular or total eclipse ends.
Eclipse
Ends
10 Partial Local Time when partial eclipse ends.
Eclipse
Ends
11 Sun Sun's altitude (in degrees) when partial eclipse ends.
Alt
12 Eclipse Eclipse magnitude is the fraction of the Sun's
Mag. DIAMETER obscured by the Moon.
For annular eclipses, it is less than 1.0.
For total eclipses, it is greater than or equal to 1.0.
13 Eclipse Eclipse obscuration is the fraction of the Sun's
Obs. AREA obscured by the Moon.
14 A or T Duration of total or annular phase
Eclipse of the eclipse (in minutes and seconds).
Duration
All times are displayed in local time using the value from the Time Zone field in Section 1 (you must add 1 hour if Daylight Saving Time is in effect). A time followed by "(r)" means the event is already in progress at sunrise. Similarly, a time followed by "(s)" means the event is still in progress at sunset. In such cases, the times and circumstances given are for sunrise or sunset, respectively. The times of sunrise and sunset are calculated when the Sun's lower limb touches the horizon.
Acknowledgments
The Eclipse Explorer is based on the JavaScript Solar Eclipse Calculator created by Chris O'Byrne and Stephen McCann. The original calculator predicts the local circumstances for any single eclipse over the period 1970 to 2039 for a geographic position supplied by the user.
The Eclipse Explorer presented here features drop-down menus for city coordinates and buttons to select any century from -1499 to 3000 (1500 BCE to 3000 CE). It can be used to explore the frequencey and circumstances of all solar eclipses visible from any location on Earth. The Eclipse Explorer was developed by Chris O'Byrne and Fred Espenak.
The Besselian elements and values of ΔT used in Solar Eclipse Explorer are the same as those used by the Five Millennium Canon of Solar Eclipses: -1999 to +3000. For the purposes of calculating eclipse circumstances from a given place, the growing uncertainty in the value of ΔT and the corresponding longitude become unacceptably large outside time period of -1499 to 3000 (1500 BCE to 3000 CE).
Permission is freely granted to reproduce this data when accompanied by an acknowledgment:
"Eclipse Predictions by Fred Espenak and Chris O'Byrne (EclipseWise.com)"